This invention relates to engine radiators, and particularly to a radiator having an integral top tank overlying the radiator coolant exit passage, whereby a barrier is provided against downflow of air into said exit passage. The invention prevents, or minimizes undesired air flow into the coolant pump, which may result in cavitation failures.
Some engine radiators of the downflow type have plural finned heat exchanged tubes (or passages.) extending between an upper tank and a lower tank. The lower tank has a coolant exit passage extending downwardly from the tank bottom wall for conveying coolant to a coolant pump mounted on the engine.
It has been found that during the engine operation air in the upper tank of the radiator can be pulled downwardly through those heat exchange tubes that are in direct vertical alignment with the coolant exit passage. Coolant pump suction draws this air from the radiator coolant exit passage through the lower radiator hose into the pump and forces it through the engine. Such airflow is disadvantageous in that it can degrade the cooling system and result in liner cavitation. Also, such air can form a vapor lock in the coolant circulation system so as to reduce coolant flow. In some cases small air bubbles can be formed in the coolant, thereby reducing the heat-absorption properties of the coolant; the coolant assumes a dark brown appearance having a reduced capability for extracting heat from the contacted engine surfaces.
The present invention contemplates the employment of a small hood in the lower tank of the radiator for blocking downward airflow into the coolant exit passage, especially during the engine start-up period. The hood is designed to overlie the coolant exit passages as to obstruct air from re-entering the cooling system via the fill line.
Specific features of the invention will be apparent from the attached drawings and description of an illustrative embodiment of the invention.